JPS6049042B2 - Hot rolling method of thin plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot thin plate rolling method that controls the plate crown (widthwise distribution of plate thickness).

One of the factors that determines the product quality of rolled materials and greatly influences the yield is plate crown, and its improvement is strongly desired. In order to significantly improve this plate crown, it is necessary to change the roll crown (usually represented by the amount of change in the roll diameter in the axial direction, that is, the plate width direction) caused by thermal expansion and wear during rolling over time. There is a need for a rolling mill that has the ability to control sheet crown, which can compensate for changes and respond to changes in rolling conditions such as rolling reduction and sheet width. In order to meet this demand, the rolling mill disclosed in Japanese Patent Publication No. 50-195-1 has been proposed as a rolling mill with extremely excellent plate crown control ability, and it is expected to achieve great results.
On the other hand, in order to fully utilize the plate crown control function of the rolling mill mentioned above and perform good plate crown control, it is essential to fully understand the deformation characteristics of the strip and to apply those characteristics skillfully. becomes.

Generally, in hot thin plate rolling, as shown in Figure 1a) and Figure 2a, the sheet crown has a medium height or a medium low height (the former is called a convex crown, and the latter is called a concave crown).

) is corrected to a rectangular shape (uniform thickness), the change is not necessarily all absorbed by the deformation in the width direction, and the deformation (elongation) in the rolling direction also appears as an average condition in the width direction. .
As a result, the strip becomes so-called wavy, as shown in FIGS. 1B and 2B, and its flatness is impaired. The state representing this flatness is called shape. In this way, the plate crown and the shape are closely related, and when controlling the plate crown, the shape must always be taken into account at the same time so as not to interfere with rolling. Now, it will be explained how the shape changes due to the above-mentioned plate crown correction in normal (tension 0) hot thin plate rolling.

In Figures 1b and 2b, the plate crown C is measured at the plate thickness H at the center of the plate width. and the plate thickness He at the end position, C=H. -Hc... (1) Represented by:

Note that when C>O, it is a convex crown, and when C<O, it is a concave crown. In order to make the handling of this plate crown correspond to the shape described later, the plate crown was modified from CH (entering plate crown) to Ch (exiting plate crown) using the ratio K to the plate thickness (referred to as plate crown ratio). The amount of change in the case of plate crown ratio change is 8K (=Kh - KH.
．． K, , KH: plate crown ratio on exit and entry sides).

On the other hand, the elongation rate is used as a measure to express the shape.
It should be noted that the case of ENT>0 is edge elongation, and the case of ENT>O is medium elongation. The difference in elongation rate on the entry side is defined as input H, the difference in elongation rate on the exit side is defined as island, and the amount of change in shape due to plate crown change is defined as A input (
= Island person H). Note that Fig. 3 is based on Fig. 1b.
A cross-sectional view when cut along the m line, Figure 4 is Figure 2b (7)
It is a view from the IV-N arrow. Using the plate crown and shape that have been quantified in this way, the fifth representative example is a study of shape changes associated with plate crown correction in normal hot thin plate rolling.
As shown in the figure.

The relationship between the plate crown ratio correction amount AK and the elongation rate difference change amount A is expressed by a straight line.

Based on the slope of this straight line, the degree of influence on the shape of the plate crown modification can be quantitatively evaluated. In addition, KA is called a shape change coefficient. In the case of Crab 1, any change in the plate crown ratio will appear as a shape, and in the case of Crab 0, no matter how you change the plate crown ratio, that is, the plate crown.
The shape is always flat.

The smaller this ratio is, the smaller the degree of deterioration of the shape due to changing the plate crown, and the easier it is to control the plate crown. FIG. 6 shows the relationship between the shape change coefficient KA determined from the relationship shown in FIG. 5 and plate thickness/plate width. From this figure, it can be seen that the thinner the plate thickness is, that is, the further the plate goes to the later stand of the hot thin plate rolling machine, the more difficult it becomes to change the plate crown significantly. This suggests that the strip crown control ability of the rolling mill cannot be fully exerted. FIG. 7 clearly shows this state. This figure shows the plate crown control amount ACh of the rolling mill in each stand when rolling is performed according to the plate thickness schedule shown in Table 1 below in a hot thin plate rolling mill configured with the above-mentioned rolling mill. ．． (=Ch.max-Ch.min) (indicated by the two-dot chain line) and within the range of allowable limit shape that does not interfere with rolling (elongation rate difference, = soil 0.22%, wave pitch 1
The plate crown amount AC (=IXI/77) (indicated by a dotted line) that can be changed by the wave height per m (approximately 3C)TW&) is shown. From this Figure 7, it can be seen that NO. l-
No. While the 3-stand can fully demonstrate the control ability of the rolling mill, the NO. 4~NO. It can be seen that the 7 stand is in a state where its control ability is being overstretched.

In particular, NO. 6~NO. When it comes to 7 stands, the rolling mill can only exhibit a control ability of 113 to 1/4. The present invention has been made in order to solve the above-mentioned problems, and in order to perform good strip crown control in hot thin plate rolling, a strip crown control method that can fully utilize the control ability of the rolling mill described above has been developed. This is what we provide.

That is, the present invention is characterized in that by performing hot thin sheet rolling under tension, the sheet crown can be changed by a large amount without significantly deteriorating the strip shape. Conventionally, in hot thin plate rolling, the tension generated due to inappropriate rolling reduction settings, inappropriate speed settings, temperature changes in the plate length direction, etc. causes variations in plate thickness and width, so it is reduced to zero or as small as possible. efforts have been made.

In this way, strip strength has rather been treated as a control disturbance. By the way, through numerous studies and experiments, the present inventors broke away from the conventional way of thinking and newly discovered that by applying tension to the strip, the amount of change in the plate crown can be increased without deteriorating the shape. This new knowledge is an extremely important basis for arriving at the present invention.

FIG. 8 clarifies the effect of strip tension on the shape change coefficient η mentioned above.

From this figure, for η, the rear tension (8 is 0.5k91T
ir1t, Δ is 1.0kgIm! t1 is 3.0k9
1Tn! It can be seen that there is no effect even if the rear tension of i) is changed, and the reducing effect of the front tension is extremely large. Also,
Front tension is approximately 1k91Tr! The advantage of the present invention is that η hardly changes when it is greater than i, and a large reduction effect is obtained in the area where the front tension is small. There are things that can be kept small. In Figure 8, the front tension where the shape change coefficient η begins to show no decrease (the limit front tension T, O in the figure) is shown.
) is approximately 1kg1Tfuft, and the present invention is characterized in that hot thin plate rolling is performed with this forward tension applied to the strip.

FIG. 9 shows the results of a relationship similar to that in FIG. 6 obtained when a critical forward tension is applied to the strip.

The solid line is the case when tension is applied according to the present invention, and the dotted line is the case when no tension is applied. From this figure, compared to the case where no tension is applied,
It can be seen that under critical forward tension, the shape change factor can be reduced to about 1 in 3 or less, so that the allowable plate crown change is increased by a factor of about 3. FIG. 10 shows the same relationship as in FIG. 7 when a critical forward tension is applied to the strip. 4~NO
．． This is for 7 stands.

The solid line is the allowable change amount of the present invention, the dotted line is the conventional allowable change amount,
The two-dot chain line indicates the control amount of the rolling mill. From this figure, it can be seen that in the limit forward tension rolling of the present invention, each stand of the hot thin plate rolling mill can fully exhibit the sheet crown control ability. FIG. 11 shows an apparatus for applying the critical forward tension of the present invention to a thin plate in a hot thin plate rolling mill equipped with a looper.

The rolling mill 5 is a six-high rolling mill in which an intermediate roll 3 whose movement can be adjusted in the axial direction is inserted between a work roll 2 and a reinforcing roll 4. I am trying to fix the plate crown. That is, in this FIG.
Reference numeral 3 denotes a front tension adjustment device consisting of a tension detector 8 for detecting front tension, a calculation unit 9, and a limit front tension setting device 10. The front tension T detected by the tension detector 8 and the limit front tension T from the limit front tension setting device 10.
The forward tension correction amount ΔT, (=Tf−T, O
is calculated, and the ΔTf is output to the looper control device 11.
Upon receiving this signal Δ, the looper control device 11 operates the looper drive device 7 to control the looper 6 to a predetermined position so that the forward tension acting on the thin plate 1 is always at the limit forward. It is made to have tension. Further, FIG. 12 shows a configuration in which the speed difference between the rolling mills 5 and 5 of FIG. 11 is adjusted to apply a critical forward tension to the thin plate 1. That is, in this embodiment, the front tension T detected by the tension detector 8 built in the looper 6 and the limit front tensions T and O from the limit front tension setting device 10 are used in the calculator 9 to calculate the front tension. Tension correction amount ΔT, (=Tf
-TfO) is calculated, the ΔT is converted into ΔV1, and the Δ■R is output to the roll drive device 14. The roll drive device 14 receives this signal ΔVR and adjusts the rotational speed of the work rolls 2, 2, thereby controlling the rolling mills 5,
By adjusting the speed difference between the two, a limit forward tension is applied to the thin plate 1. On the other hand, in Fig. 13, the speed difference between the rolling mills 5 and 5 is adjusted without using the looper.
A limit forward tension is applied to the thin plate 1.

That is, in this embodiment, in the arithmetic unit 9,
The front tension correction amount ΔT, (=T
f−T,O) and convert the ΔT to Δ■8,
Output to the roll drive device 14. Then, this roll drive device 14 receives this signal ΔVR and drives the work rolls 2, 2.
The rotational speed of the rolling mills 5 is adjusted, thereby adjusting the speed difference between the rolling mills 5 and 5, so that a critical forward tension is applied to the thin plate 1. In addition, this figure 11 to 13
The hot thin plate rolling mill 5 shown in the figure is a 6-high rolling mill.
Of course, it may be configured as a high rolling mill.

As explained above, according to the method of the present invention, the amount of plate crown correction can be increased to about three times that of the conventional method within an allowable range that does not impede the rolling work of the strip shape, and the rolling process allows for large correction of the plate crown. The control ability of the machine can be fully demonstrated. Furthermore, it is possible to easily manufacture a strip with a desired plate crown, and in addition, many other effects can be obtained, such as the ability to improve the yield of strip products.

[Brief explanation of drawings]

Figures 1A, b and 2A, b are views showing the states of the strip before and after rolling, respectively, and Figure 3 shows the state of the strip before and after rolling.
A cross-sectional view when cut along the line, Figure 4 is from ■-■ in Figure 2b.
Fig. 5 is a relationship diagram between plate crown ratio correction amount and elongation rate difference change amount, Fig. 6 is a relationship diagram between plate thickness/plate width and shape change coefficient, and Fig. 7 is a graph showing the relationship between plate crown ratio correction amount and elongation rate difference change amount. A diagram showing the plate crown control amount of the rolling mill and the allowable plate crown change amount within the range that does not hinder the rolling operation due to shape deterioration in thin plate rolling. Figure 8 shows the effect of reducing the shape change coefficient of front tension. The diagrams shown, FIG. 9 is a relationship diagram between plate thickness/width and shape change coefficient in the rolling process using the limit forward tension of the present invention, and FIG. 10 shows the hot thin plate subjected to the limit forward tension of the present invention. Figures 11 to 1 are diagrams showing the plate crown control amount and allowable plate crown change amount of the rolling mill in the subsequent stand in rolling.
FIG. 3 is a simplified configuration diagram showing a means for applying the critical forward tension of the present invention to a strip in a hot thin plate rolling mill. 1...Strip, 2...Work roll, 3...Intermediate roll, 4...Reinforcement roll, 5
...Rolling mill, 6...Looper, 7...
... Looper drive device, 8 ... Tension detector, 9
......Calculator, 10...Limit forward tension setting device, 11...Looper control device, 12...
- Tension detection roller, 13... Front tension adjustment device, 14... Roll drive device.

Claims (1)

[Scope of Claims] 1. In a rolling method for controlling the plate crown of a hot thin plate, the shape is deteriorated by applying a forward tension to the thin plate that exceeds a limit at which the degree of influence on the shape by plate crown modification no longer changes. A hot thin plate rolling method characterized in that a large amount of sheet crown correction can be obtained without causing any damage to the sheet crown. 2. The method of hot rolling a thin sheet according to claim 1, wherein the means for applying a critical forward tension to the thin sheet is to adjust the position of the looper of the thin sheet. 3 Set the value of the limit forward tension to be applied to the thin plate, detect the forward tension applied to the thin plate, and adjust the looper position based on the difference between the detected forward tension and the limit forward tension. 3. The method of rolling a hot thin plate according to claim 2, wherein: 4. The method of rolling a hot thin plate according to claim 1, characterized in that the speed difference between a plurality of rolling mills is adjusted as a means for applying a critical forward tension to the thin plate. 5 Set the value of the limit front tension to be applied to the thin plate, detect the front tension applied to the thin plate, and rotate the work roll based on the difference between the detected front tension and the limit front tension. 5. The method of rolling a hot thin plate according to claim 4, wherein the speed is adjusted to adjust the speed difference between the plurality of rolling engines provided.